91098781 has 2 divisors, whose sum is σ = 91098782. Its totient is φ = 91098780.

The previous prime is 91098731. The next prime is 91098829. The reversal of 91098781 is 18789019.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62647225 + 28451556 = 7915^2 + 5334^2 .

It is an emirp because it is prime and its reverse (18789019) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91098781 - 2¹³ = 91090589 is a prime.

It is a super-2 number, since 2×91098781² = 16597975799371922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91098731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45549390 + 45549391.

It is an arithmetic number, because the mean of its divisors is an integer number (45549391).

Almost surely, 2^91098781 is an apocalyptic number.

It is an amenable number.

91098781 is a deficient number, since it is larger than the sum of its proper divisors (1).

91098781 is an equidigital number, since it uses as much as digits as its factorization.

91098781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36288, while the sum is 43.

The square root of 91098781 is about 9544.5681410947. The cubic root of 91098781 is about 449.9568370123.

The spelling of 91098781 in words is "ninety-one million, ninety-eight thousand, seven hundred eighty-one".